The overall objective of this proposed research is to define the chemistry of solution catalyzed disulfide cleavage. Several chemical aspects of the catalyzed disulfide reversibly yields dithiol redox interconversion, which are relevant to the enzymatic reaction of "reactive" disulfides, will be studied in chemical model reactions. Specifically, the objectives can be stated as follows: 1) Investigation of the Importance of General Acid Catalysis in Activation of a Disulfide toward Nucleophilic Cleavage. 2) Investigation of Direct Hydride Transfer as a Mechanism for Disulfide Reduction.